This invention relates to gas lasers of the transversely-excited type.
In the development of transverse-excitation lasers, many of which operate at or near atmospheric pressure and thereby permit generation of substantial volumetric output power, a variety of techniques have been developed in an attempt to assure predictable, repeatable operation of the laser. These techniques are directed to the problem that at the start of a pulse in a transverse-excitation laser the medium may not break down uniformly, but may develop arcs at various locations in the transverse discharge.
Another problem common to many high-pressure molecular gas lasers is that the optimum field for excitation is lower than that required to break down the gas to create the discharge.
One technique used to overcome these problems has been to preionize the medium with an electron beam generated externally and injected into the laser-active medium. This technique is commonly described as the E-beam technique.
The other, more commonly used, technique makes use of ultraviolet radiation to preionize the laser medium. The ultraviolet radiation may result from a preliminary discharge of some type, for example, a small arc discharge from one or more trigger electrodes, or may be ultraviolet radiation from some external source.
Both of the foregoing techniques have advantages and drawbacks. The E-beam technique is much more easily extended to large, high power, high pressure lasers than the ultraviolet preionization techniques but it is also much more cumbersome and less attractive for most commercial applications.
A need clearly exists for a technique as simple and compact as the ultraviolet preionization technique but which also has the reliability and possibility of extension to higher operating pressures and output powers, such as is characteristic of the E-beam technique.